U.S. Pat. Nos. 3,274,209 and 3,364,112 to Raeymakers et al, assigned to Janssen Pharmaceutical N.V. disclose 6-substituted-imidazo[2,1-b] thiazole compounds, compositions containing same, and their use as anthelmintic agents. These compounds have the following structure ##STR2## wherein the dotted line between the 2- and 3-positions represents an optional bond, and Ar is a member selected from the group consisting of thienyl, furyl, phenyl and substituted phenyl in which said substituent is a member selected from the group consisting of halo, preferably chloro, bromo and fluoro, nitro, amino and trifluoromethyl; naphthyl, preferably .alpha.-naphthyl; and benzyl; provided that, when said Ar is benzyl, a saturated bond exists between the 2- and 3-positions of the imidazo [2,1-b] thiazole nucleus.